Breast cancer is the most commonly occurring cancer in US women. Breast cancer incidence is greater in Black than White women before age 45 and lower at older ages, however mortality from breast cancer is greater in Black women than White women at all ages. Several epidemiological studies have shown an association between obesity and breast cancer risk. Obesity is inversely associated with premenopausal breast cancer risk, while the opposite is true for postmenopausal breast cancer risk. Abdominal obesity in particular is associated with increased breast cancer risk. Being overweight/obese is also associated with poorer breast cancer prognosis. Obesity has achieved epidemic proportions in the US and is a major public health issue. Furthermore, 280,000 deaths/yr are attributed to obesity. Black women are more likely to be obese than Whites, with 80% of Black women >40 yrs of age being overweight or obese. Obesity was associated with an advanced stage of breast cancer at diagnosis in Black compared to White women. The ACS Cancer Prevention Study II found that breast cancer mortality rates increased continually with increasing BMI. Breast cancer is the most common cancer in women worldwide, accounting for -23% of all cancer cases in women. Furthermore, age-adjusted incidence rates for breast cancer are increasing in most countries around the world. Interestingly, the increase parallels the increases in lifestyle-related diseases such as type 2 diabetes, obesity, and metabolic syndrome.